Seven biggest storms to hit Wellington

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New Zealand must accept the possibility of dramatic changes to its climate, instead of continuing to build homes in areas that may not last another generation.

Victoria University's Martin Manning, who ended his tenure this week as director of the Climate Change Research Institute, is calling for New Zealand to end its "inertia" and prepare for the impact of events such as storm surges and sea level rises.

Professor Manning's comments come at the end of a week when scientists gathered in Wellington for the Extreme Weather 2011 conference, where experts discussed whether extreme conditions could be expected to become more frequent as a result of expanding settlement, higher temperatures and climate change.

Scott Power, senior principal research scientist at Australia's Bureau of Meteorology, said the past decade had been the world's warmest on record, and last year was among the three warmest years on record.

It was inevitable there would be further warming and sea level rises, but the extent of extreme weather events would also depend on natural factors such as weather systems, Dr Power said.

This year's strong La Nina weather system had coincided with the damaging cyclone Yasi, and extensive Queensland floods - just as bad flooding hit Australia in the 1974 La Nina.

Professor Manning said the recent storms were different because, at the same time, hundreds of people were killed by floods in Brazil and Sri Lanka. These events came only months after extremely cold temperatures froze the northern hemisphere, and the Amazon reached its lowest levels on record.

"Patterns of extreme events are happening across the planet at the same time."

The world was "perhaps in more trouble" than scientists had thought. "We are now starting to see the potential of human-driven climate change to be doing very dramatic things is very serious."

Although scientists were "always conservative", a broader perspective needed to be taken now of how to deal with future extreme weather events.

The private sector, such as the insurance industry, was already considering this - but Professor Manning accused New Zealand of failing to act in some areas.

For example, decisions were being made to allow building on low-lying land. "In the meantime, this guy can build his bach here or this guy can build a house on stilts.

"We've got subdivisions, hundreds of millions of dollars of investment gone into it, and it may not last a generation."

National Institute of Water and Atmospheric Research risk engineer Stefan Reese said Niwa and GNS Science were working on the Risk Scape project, which gathered information on various hazards, including possible effects of climate change. Last year, Dr Reese said there were 950 disasters around the world, of which nine out of 10 were weather-related.

Professor Manning said New Zealand needed to form alliances with developing countries that were moving faster in seeking solutions. South Korea, for example, was harnessing energy from tides and China was pushing ahead with renewable energy projects.

April 10, 1968: Cyclone Giselle caused peak gusts of 145 knots (270kmh) near Wellington, after colliding with an Antarctic storm moving north. Giselle led to the sinking of the interisland ferry Wahine, and the loss of 51 lives. Total damage caused by the storm was estimated at $14 million.

December 20, 1976: Heavy rain caused widespread flooding and landslides in Wellington City and Hutt Valley. Hutt River burst its stopbanks and workers in Petone took refuge on factory roofs. Landslides destroyed houses and a boy was killed by a collapsing wall when a slip struck a hall in Crofton Downs. More than 350mm of rain fell in 24 hours.

4 October, 1997: More than 60 homes were flooded and residents in Lower Hutt riverside areas were evacuated during downpours. Two people died, and isolated landslips closed some Wellington roads and parts of State Highway 1.

26 June, 1998: A firefighter works to empty out a car parking building which flooded during heavy rain. A severe thunderstorm affected Karori and Kelburn, with rain breaking all previous records and falling at a rate with a return period of well over 200 years. Rainfall at Kelburn totalled 69.5mm between 7.35pm and 9.10pm.

October 13-27, 1998: Gale force northwesterlies blew throughout the lower North Island. On October 18, gusts of 183kmh were recorded at Castlepoint. Winds were most severe on the following two days, when a gust of 215kmh was recorded on a Wairarapa farm. A truck was overturned, ships ripped from their moorings in Wellington, and some houses lost their roofs.

January 10, 2002: Thunderstorms over Wellington resulted in torrential rainfall, about 40mm in 30 minutes, and flash floods in the city centre. Similar storms some with hail and surface flooding also happened in Whanganui, Manawatu, the central and eastern North Island, Buller and Nelson. The average recurrence interval of this rainfall event is more than 100 years.

February 14-16, 2004: The Valentines Day storms left hundreds of people homeless, and silt and floodwaters inundated considerable areas of farmland. Many rivers breached their banks, bridges were damaged and stock was swept away by floodwaters. A civil state of emergency was declared in Whanganui, Manawatu and Rangitikei. About 500 Lower Hutt residents were evacuated because of floodwaters. ntsGand many commuters were unable to enter Wellingtonnte The event produced galeforce southerlies, with gusts of 230kmh in the Tararua Range, and swells of 11m in Cook Strait.